It's also possible that Facebook determined that this person has substantially different politics than you, and has put you in different 'boxes'. You can actually check what groups Facebook thinks you belong in. For instance, Facebook thinks my peer group is 'Starting Adult Life', and my US Political Stance is 'very liberal'.
(Facebook also thinks I work in a production occupation, like mining, or lumber, which couldn't be further from the truth, which explains all the ads for industrial equipment)
I went to high school in a really conservative place, and I'm friends with a lot of people who have wildly different views on religion and politics. A few years ago I stopped seeing their posts, even if I added them to the group of people I see first on Facebook. Meanwhile, I started seeing a ton of posts from people who I barely knew in college, presumably because their 'beliefs' were much closer to mine.
I'm extremely cynical, and I find dogmatic people of similar beliefs as annoying as people whose beliefs I disagree with, and my Facebook feed became a personal hell of dogmatism, especially leading up to the 2016 election. As a result I check Facebook at most once a week. It's entirely possible that leaving the platform improved the experience for some of my more conservative peers from high school, who no longer have to see my posts on the walls of mutual friends.